Liquid crystal display elements are now widely used in display unit in electronic office system such as word processor, lap-top computer, etc. The element comprises a liquid crystal phase sandwiched between transparent substrates such as glass or plastic substrates with transparent electrode films. When voltage is applied between the two electrodes using single matrix or active matrix, information such as an image is displayed. As the methods to accomplish the purpose, there are a method using dynamic scattering operated by typical TN type on STN type or other current effect, a method utilizing phase transition of cholesteric-nematic, and a method combining macromolecule with liquid crystal.
In the element, which comprises nematic liquid crystals dispersed and fixed on macromolecular resin, refractive index of liquid crystal is equalized with refractive index of macromolecular resin, and voltage is applied to align orientation of liquid crystal substance in voltage-applying direction and to turn it to transparent state. When voltage is not applied, orientation of liquid crystal substance is not aligned, and light is scattered in boundary surface between liquid crystal substance and macromolecular resin or in the dispersed and fixed liquid crystal phase, thus turning it to non-transparent state. As a result, display is accomplished by utilizing transparency and non-transparency. The liquid crystal element, which comprises nematic liquid crystals dispersed and fixed on macromolecular resin, is characterized in that the area is large, response time, particularly falling time, is short, polarizing plate is not required and light utilizing efficiency is high, vision angle is wide and uniform, or it is flexible. Accordingly, it is used in light-adjusting sheet for window or in projection type display.
It is also extensively used for projection type display or computer display, and it is more advantageous than TN type or STN type display because falling time is as short as 1 to 30 ms. Such liquid crystal display element is sandwiched between electrodes, and AC voltage is applied, and display and erasing are performed by turning on and off. In this case, hysteresis occurs in voltage vs. light transmittance, and it is reported that there are some differences in transmittance between AC voltage increase and voltage drop. When AC voltage is turned off, or when no voltage is applied, it is turned to the initial transmittance, i.e. non-transparent state.
As the method to display information such as image, a method to sandwich the element between matrix electrodes and to perform display by turning voltage on and off for each pixel is generally used, while image-like pattern electrodes are also used. Also, there is a method, in which, when composite film of macromolecule and liquid crystal is formed, image-like ultraviolet ray is irradiated using UV-setting type macromolecular material. In any case, fixed information is flashed on and off. On the other hand, as the element with memory property, there is the one utilizing cholesteric-nematic phase transition. In this method, liquid crystal is sandwiched between transparent electrodes.
It is an object of the present invention to provide an information recording medium, which has an information recording layer laminated on an electrode layer and is used for recording electrostatic information in visible state, and which can provide permanent recording in visible state, and also to provide a method for recording and reproducing such information.